Trigger Points in the Masticatory Muscles in Subjects Presenting with Ankylosing Spondylitis

Abstract

Objective: This paper describes differences in both the presence of trigger points [TrPs] in the masticatory muscles and active mouth opening between subjects with ankylosing spondylitis [AS] and normal healthy control [HNC] subjects. In addition, we assessed the possible correlations between TrPs in the masticatory muscles, active mouth opening, cervical flexion-extension motion, and occiput-to-wall distance.

Methods: Twenty subject with AS and 20 matched HNCs participated in this study. One clinician, blinded to the subjects' condition, examined first for TrPs. Trigger points were identified by eliciting referred pain with palpation and increased referred pain with muscle contraction. A second clinician assessed the active mouth opening, the cervical motion in flexion-extension, and the occiput-to-wall distance measurements.

Results: Ankylosing spondylitis subjects showed a greater number of TrPs than HNCs [P < 0.001]. Patients showed a more reduced mouth opening and cervical mobility than HNCs [P < 0.001]. Within the AS group, there was a positive association between the number of active TrPs and occiput-to-wall distance [r_s = 0.6; P < 0.001], and between mouth opening and cervical mobility [r_s = 0.8 in flexion, r_s = 0.65 in extension; P < 0.001]). A negative correlation was found between mouth opening and occiput-to-wall distance [r_s = −0.75; P < 0.001] and between mouth opening and the total number of TrPs [r_s = −0.5; P < 0.001].

Conclusion: Trigger points in the masticatory muscles were more conspicuous in AS subjects than in HNCs. Patients showed a reduced active mouth opening and cervical flexion-extension motion than matched HNCs. The AS subjects with lesser mouth opening showed a greater occiput-to-wall distance and a greater number of TrPs in the masticatory muscles.

KEYWORDS:

• Ankylosing spondylitis
• masticatory muscles
• trigger points
• active mouth opening
• occiput-to-wall distance